The present invention relates to direct injection fuel injectors; more particularly, to such fuel injectors having both opening and closing solenoid actuators; and most particularly, to such a fuel injector having reduced size, lower component cost, fewer assembly steps, lower material cost, single flow assembly, and external calibration.
Outwardly-opening fuel injectors are well known for use in injecting fuel into the combustion cylinders of internal combustion engines. Such injection is known in the art as xe2x80x9cdirect injectionxe2x80x9d as opposed to xe2x80x9cport injectionxe2x80x9d wherein fuel is injected into a manifold port upstream of the cylinder""s intake valve.
An especially demanding use of direct injection is for injection of gasoline into spark-ignited internal combustion engines. Engine manufacturers are now recognizing that so-called xe2x80x9cspray-guidedxe2x80x9d fuel injectors can be important factors in meeting fuel emission and fuel economy standards. Spray guided means that the fuel is injected into the combustion chamber and presented to the spark plug for ignition as an atomized fuel cloud having the proper location, size, and shape. The actual combustion chamber itself is not required to deflect, relocate, or prepare the fuel for ignition. For spray guided combustion, it is very important that the spray geometry remains consistent throughout a wide range of engine operating conditions. A known method of achieving the spray guided function is to cause the fuel injector to open outwardly into the firing chamber and to use the valve head to shape and direct the fuel exiting the injector.
U.S. Pat. Nos. 6,036,120, issued Mar. 14, 2000, and 6,065,684, issued May 23, 2000, are drawn to apparatus and method, respectively, for a direct injection fuel injector and are both incorporated herein by reference. The specifications are identical, and the two patents are treated here as a single disclosure. A high fuel pressure exerting an opening force is slightly overbalanced by a return spring tending to close the valve. A first solenoid acts to open the valve against the excess return spring force and a second solenoid acts to close the valve when the first solenoid is de-energized. Rapid valve closing is provided by energizing the second solenoid before de-energizing the first solenoid, the force of the second solenoid when the valve is open being insufficient to overcome the force of the first solenoid holding the valve open. Thus, the second solenoid magnetic force is fully developed and quickly closes the injection valve when the first solenoid is de-energized.
The prior art fuel injector has several drawbacks relating to final size, placement of the solenoids within the fuel flow path, and ease of assembly.
What is needed in the art is a dual-coil, outwardly-opening fuel injector having fewer components, solenoids outside a fuel tube, and which is easier to assemble.
It is a principal object of the present invention to reduce the size and cost of an improved dual-coil outwardly-opening fuel injector.
It is a further object of the present invention to simplify the assembly of such an improved fuel injector.
It is a still further object of the present invention to provide for external calibration of the return spring of such an improved fuel injector.
Briefly described, a dual-coil outwardly-opening fuel injector includes a fuel tube connected at a lower end to a lower injector housing. Within the fuel tube are a lower (opening) solenoid pole piece, a specially-formed armature, and an upper (closing) solenoid pole piece. A seat assembly including an injector nozzle, swirler, and valve seat are adjustably threaded into the lower housing. A pintle assembly, including a solid pintle portion supporting a valve head and a tubular portion-welded thereto, is axially disposed within the fuel tube and those components and is welded to the armature which is temporarily spaced from the upper pole piece by a distance equal to the opening stroke of the valve. The seat assembly is then turned into the lower housing, moving the armature away from the lower pole piece and into contact with the upper pole piece, thus setting the stroke of the valve. A return spring adjustment mechanism disposed on the upper pole piece engages the upper end of the pintle assembly for varying the closing force of the return spring. Opening and closing solenoid preassemblies are mounted external to the fuel tube for magnetically engaging the pole pieces and armature within in known fashion.